High-Performance\nSelf-Powered WSe₂/ReS₂ Photodetector Enabled\nvia Surface Charge Transfer Doping

Abstract

Two-dimensional (2D) van der Waals heterostructures based\non various\n2D transition metal dichalcogenides are widely used in photodetection\napplications. However, their response time and photoresponsivity are\nlimited, posing a challenge for their applications in high-sensitivity\nphotodetection. Surface charge transfer doping (SCTD) has emerged\nas a novel doping approach for low-dimensional materials with high\nspecific surface area and attracted considerable attention, as it\nis simple and effective, does not damage the lattice, and considers\nvarious types of dopants. Herein, we prepare p–i–n junction-based\nphotodetectors via the SCTD of WSe₂/ReS₂ heterojunctions\nusing p-type dopant F₄-TCNQ molecules, where doped WSe₂ serves as a p-type semiconductor, undoped WSe₂ acts as an intrinsic layer, and ReS₂ functions as an\nn-type semiconductor. The surface-charge-transfer-doped WSe₂/ReS₂ heterojunction leads to a reduction in the Schottky\nbarrier and an increase in the built-in electric field compared with\nthe as-fabricated heterojunction. In the photovoltaic mode and under\n785 nm laser illumination, the photodiode exhibits an increase in\nresponsivity from 0.08 to 0.29 A/W, specific detectivity from 1.89\n× 10¹² to 8.02 × 10¹² Jones, and the\nexternal quantum efficiency from 12.67 to 46.29%. Additionally, the\np–i–n structure expands the depletion region width,\nresulting in a photovoltaic response time of 7.56/6.48 μs and\na −3 dB cutoff frequency of over 85 kHz, an order of magnitude\nfaster than the pristine response time. Herein, we derive an effective\nand simple scheme for designing high-performance, low-power optoelectronic\ndevices based on 2D van der Waals heterostructures.